The strings in a racket are imparted at the manufacturer or during restringing a predetermined tension. This tension can vary, depending on the individual desires of stringer, the equipment used and his consistancy. The varying of tension from one stringing to another will noticeably alter the playing characteristics of the racket. Over the course of time the tension of the racket strings will decrease due to the repeated impacts of balls hitting the strings, temperature fluctuations and by ageing. Modern tennis rackets may be strung at tensions of between 30 and 85 pounds. Depending on the time between stringing and the time of use the original tension may be considerably different. There is a need to be able to adjust the tension of the present strings to accomodate the immediate needs of the player. Proposals have been made to build-in devices for the purpose of retensioning the strings of rackets. These devices are relatively heavy and require a racket of a special design.
Another approach has been to add devices to the strings on the playing face of the racket after the stringing or restringing of the racket. One such device is the invention U.S. Pat. No. 4,512,576. That invention requires the application of the tensioning device be on the playing face of the racket where it can interfere with the play of the ball. It is also extremely heavy, making claims of eight to ten grams. In contrast the present invention may weigh less than one gram.
Previous inventions have not allowed for the rapid change of string tension during play. It has been common practice for players to have several rackets strung at slightly different tensions prior to important matches so that at the time of the match variations in the tensions of the strings can be compensated for by selecting the racket that has the right feel.
It has also become common for players to use one racket while serving points and another while receiving service points, the two rackets strung at different tensions to the specifications of the player. The present invention aleviates the need for several rackets. The present invention allows the player within seconds, even between points and without leaving the field of play, to alter the tension of his racket strings either downward or upward to suit his plan of play.